This invention relates to a storage system for storing data in a plurality of disk drives.
There has been known a so-called storage system, whose subsystem is composed of a disk array composed of a plurality of disk drives, for storing data to the disk array.
The storage system is composed of a host interface, a disk interface, a cache memory, a control unit, and a switch for connecting them. The control unit is composed of a processor and a control memory for storing control data of the processor for example. The storage system is connected with a host computer via the host interface and with the disk array via the disk interface. The storage system is composed of the host interface for connecting with the host computer, the disk interface for connecting with the disk array, the cache memory for quickly executing data access to/from the disk array, a CPU for controlling the storage system, the switch for connecting each unit within the storage system, the control memory for storing data required by the CPU in making the above-mentioned control, and a bus used by the CPU in accessing the memory.
Large corporations typified by banks, security companies, telephone companies, and the like are inclined to cut costs required for operations, maintenances, and administration of computer and storage systems by centralizing within a data center the computer and storage systems conventionally scattered at various places. Therefore, it is now required to manage a larger scale data by one storage system.
Still more, due to multi-functioning of the storage system, a rate of control data tends to be larger as compared to user data actually sent from the host computer.
Up to now, there has been known a storage system in which whole control data is stored in a control memory of a control unit independent of a cache memory as disclosed in JP 2004-240949 A for example.
Meanwhile, there has been known a storage system using a general purpose server that has a dedicated interface and a hard disk as destinations in saving the control data and that is capable of handing control data whose volume is larger than a capacity of a control memory as disclosed in “The IBM Total Storage DS8000 Series Concepts and Architecture” Page 64, Line 6, “online” Retrieved on Aug. 31, 2006, Internet, (http://www.redbooks.ibm.com/redbooks/pdfs/sg246452.pdf.)